1. Field of the Invention
The present invention relates to a process for foam treating pile fabrics, especially carpets, and to a foam applicator device which may be used in such a process. More particularly, this invention involves foam treating a carpet by applying a foam composition through the backing of the carpet.
2. Description of Related Art
It is well known to apply "foam compositions" to the facing of pile fabrics, such as carpets. By the term "foam composition" or "foam", it is meant a stable foam composition which contains chemical treating agents, such as, e.g., dyes, antistatics, stain resist agents, and fluorochemicals, and mixtures thereof.
Generally, the use of a foaming medium is an effective means for applying treating agents, since it reduces water usage, energy required to heat the carpet for promoting setting of the agents, and effluent streams which require waste treatment or contribute to overall pollution from the process. Various types of equipment, such as the one described in U.S. Pat. No. 4,576,112 to Funger et al., apply foamed agents to the face of a carpet with a resilient seal pressed against the backing of the carpet to promote sealing. Such equipment is presently in commercial use to foam apply both fluorochemical and stain resist agents to the facing of carpets.
These techniques and equipment are considered improvements over such ones, as described in U.S. Pat. No. 4,193,762 to Namboodri et al., and U.S. Pat. No. 4,275,683 to Kutz et al., where foam is cast onto one or both sides of a carpet and calendered into the surface by rolls or other pressure application means.
However, conventional methods have several disadvantages. For instance, at wet pick-up levels (the ratio of the weight of the liquid applied to the dry weight of the carpet.times.100) less than 100%, the porosity of the carpet, when compressed by all known methods, is low and foam penetration into the carpet, especially heavy weight carpets, is only 50 to 70% from the point of application to the deepest point in the carpet face. As carpet density and pile volume increase, the ability of conventional methods to uniformly distribute the foam throughout the carpet is even further reduced.
Some proposed solutions to this problem of completely and uniformly distributing treating agents into the carpet do not even involve foam application.
For example, one method commonly used for applying the treating agents involves flooding the agents onto the surface of a carpet at wet pick-up levels greater than 350%. Currently, the most effective equipment used for applying stain resist agents is the Flexnip, produced by Edward Kusters Machinenfabrik, Gladbacher Strasse, Krefeld, Germany. Treating agents applied by this type of process are substantially 100% distributed throughout the carpet by raising wet pick-up levels to the point where excessive fluid exists. The excessive fluid distributes the chemicals as it flows across the face of the carpet during application, or as it traverses the fiber tufts. However, this process uses excessive amounts of energy and water and requires extracting excess stain resist agents before the carpet is dried. As a result, unacceptable levels of effluent which must be treated are formed.
In other cases, the carpet mills currently apply treating agents by spraying or foaming the agents onto the face of the carpet after the washing and extraction steps. These techniques, commonly used for applying fluorochemicals, result in uneven distribution of the chemicals through the carpet, with the majority of the chemicals being concentrated along the upper half of the tuft. For spray systems, treating agents are concentrated in the upper 20% of the tuft lengths. As a result, a considerable amount of the chemicals is lost in the shearing step during final finishing of cut pile carpets.
Clearly, there is a need to develop an improved means for adding dyes or post dye chemical treating agents to carpets. A desirable process would require less water and energy, reduce effluent streams, and improve the distribution and uniformity of chemical application. Foam application, at low wet pick-ups, offers the best approach to achieve these desired benefits, provided it is uniformly applied. The present invention provides such a process, wherein the foam is applied through the carpet backing at low wet pick-ups and uniformly and completely penetrates throughout the carpet. This invention also includes a new foam applicator apparatus.